The following URL will allow you to change your selection:
https://vcl.ncsu.edu/scheduling/index.php?mode=selectauth&clearselection=1

This is often caused by using Back/Forward in certain web browsers (particularly Safari on Macintosh).

In order for the web application that is the scheduling interface for VCL to work correctly it must know what web page you were referred from when showing you any page except for the entry page. Some web browsers (Safari in particular) tend to forget exactly how you came to a given webpage. Thus when your web browser tries to load a given page in the scheduling interface and cannot remember how you can to be at that page, the scheduling web application sends you back to the entry page.